AMPL > >Errors and Messages > >What does AMPL mean by “syntax error”? I double-checked the offending statement in the AMPL book, and my syntax is fine.

AMPL is signaling an invalid statement of some sort, but the error may not be a matter of “syntax” in the usual sense. For example, you could be trying to define a set index at a place where it is already in use:

ampl: display {i in ORIG}:
ampl?    supply[i] * sum {i in DEST} cost[i,j];
syntax error
context:  supply[i] * sum {i  >>> in  <<< DEST} cost[i,j];

The index i cannot be defined following sum, because it is within the scope of the index i that was defined following display.

If you receive a syntax error that is particularly hard to interpret, please let us know.

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